Vibrations and power issues.

[sportfishermanssvc]

Looking for a little help. First a little background. This is my first summer running my 1978 Trojan F25. I am a marine mechanic and have worked on boats since I was a kid, that said I have 0 experience with Inboards, everything I have ever worked on has been I/O or outboard.

I have only managed to get in three trips with my trojan so far this year, at low speeds she runs like a dream, runs smooth, quiet and vibration free. As soon as you start powering up the noise and vibration grows. At full throttle it gets to the point that you have to shout to hold a conversation and the vibration actually moves stuff around that is sitting unsecured in the boat. I dont know if this is normal or not but would like to do something about it if I can. I inspected the prop and as far as can tell it is in good shape, I definitely dont see anything that should cause severe vibrations.

So what are areas for me to begin looking, I am sure there are bearings or bushings that can go bad in the transmission and along the prop shaft, but i dont know where to begin and hate to start just tearing in without direction.

Also any ideas on top speed for this boat? I can barely squeeze 25 out of it and it just feels like it is being held back. If it is in my head I will leave it be, otherwise I will start digging deeper.

[jav]

Here's what I'd check if you've already had the prop checked (visual inspection won't tell you much):

1) shaft / engine alignment
2) shaft striaghtness
3) cutlass bearing
4) engine mounts

[RWS]

JAV is right on.

Here's some additional items. If the props are running too close to the hull you'll get the same effect.

Also check to see if the engines are making thier required WOT RPM. If not you may have a combination of issues creating this problem. Do both engines have the same WOT RPM? Does shutting down one engine over the other appreciably change the vibration ?

Could be the props have a diameter that is too big. That would cause the WOT RPM loss & the vibration if they're getting close to the hull.

LOTS of stuff to check out.

RWS

[randyp]

Definitely check shaft alignment and cutlass bearing. Even without the vibration these boats are NOISY! The engine is right under the cockpit floor and the muffler (better check that) is also right under the floor. If there is no soundproofing it gets real noisy, especially over 3000 rpm. 25 mph should be top end for the Chysler 318-225 hp if that's your engine. WOT RPMS should be 4200.

Hope that helps

Randy
1977 F-26 "Blue Heron"

[Danny Bailey]

If your rudder shaft is loose in the stuffing box/bearing piece that bolts to the bottom of the boat and the rudder can shake sideways from the prop pulses it will make an awful racket. I had this problem on a '73 Chris Craft 28 footer. I tightened the crap outta the stuffing box and it stopped the noise.

[jayn8yy]

i also am a farely new owner of an F25 78' - i re-did the entire engine Ford V8, everything. new cylinders, valve job, manifolds, risers, pretty much did everything except the block ( which i checked ). anyway - i dont get speed out of her, she seems best just at a nice low rpm - cruising - i run her out of south florida, in the ocean and the ICW. i spoke to a few people and everyone i have spoken to seems to say the same thing - the boat is at is best at lower speeds. i have control issues and the thing shakes like hell at anything over 15 knots ( 3000 rpm ). if you have any luck with anything let me know. currently, i am redoing the cabin and galley area. all in all i am very happy with the boat -- except she is not built for any speed it seems and is really noisy.

[GailWitch]

new owner of a trojan f26 1979, same issue but with ticking. Any help on the ticking, looking into other previously said items.


mike

[randyp]

For the record, my 1977 F-26 with original Chrysler 318, drive train, shaftl prop, etc will run smooth and up to 25 mph at WOT when it's just me on the boat and not loaded up with all sorts of cruising goodies, food, beer, etc. That's on a smooth surface. And, yes, it's noisy, since I'm sitting or standing on top of the engine and there is NO soundproofing over it. The vibration is going to be result of: shaft, prop, engine mounts, and/or all of the above.

[Stripermann2]

Jav hit the highlights of what to check.

If out of the water, pay attention to the prop. If you take a carpenter's square and clamp it to the rudder and set it close to the blade edge, rotate the prop slowly, it should have the same run-out on all blades and not hit or vary much. props will give a bad vibration if out.

Check the shaft coupler to trans coupler for being mated absolutely square. This is where engine alignment is very important.

Also, be sure the engine performance is right on...an 8 cylinder, running on 7 cylinders due to weak compression or fouled plug will vibrate as well even if no other engine issues seem prevelant.

Boats are not like automobiles. There is no down hill for boats, they are always uphill so to speak and under load. Unfortunetly, unlike a car where you can tweak this or that, shut the hood, go around the block and it's fixed, boats' don't afford that luxury!

[MattSC]

Striperman hit it right on the head, check the prop runout like he described. Any variance and you'll have a vibration. Something else to check is make sure if you have any zincs on the shaft that they are tight, and not loose, this could also cause a vibaration, other things to check are the shaft, cutlass bearing and engine alignment.
Your top speed seems about right, I have a 75 F-26, and I would hit 25 at WOT (4000rpm) according to gps with a lm318. With my new engine I hit 31.7 knots according to the GPS at WOT, but I only operate it at 17kts or so, that is the boats sweetspot. It is a loud boat, but If everything is aligned and the prop is good you shouldn't experience any vibrations.

[David Kane]

GailWitch: Stripermann2's post about low compression/fouled plugs may have a bearing on your ticking noise. Do you hear it when you 1st put your engine into gear, then don't hear it at higher rpm's? That was one of the issues I had with my starboard engine (Mercruiser 255, based on the GM 350, or 5.7l, engine). Found I had a piece of the #1 cylinder exhuast valve broken off, resulting in zero compresson on that cylinder. I'd earler addressed a fouled plug situation. Those kinds of things will contribute to the engine running rough and creating a gear lash noise. When I relaced the heads & got rid of the fouled plugs, no more ticking noise.

[jddens]

My 1972 30' Fly Bridge Sea Raider has Merc FI 350's, 330hp ea and my cruise RPM's are simular to yours. With clean bottom and light load I get about 20 knots at 3000-3100. WOT about 28-30 knots. Most ecomomical cruise is about 8 knots (hull speed).....love this boat!!!

[captainmaniac]

Mike - Don't know if this will help... I copied it from a post I had in another thread...

I may be taking this thread in the wrong direction, but here is Water Music's 'speed curve'... is this in line with what you other F32 owners with 360s are seeing? I have over 1570 hrs on the engines, they are almost 30 years old, and I don't know for sure how the previous two owners treated her the first 21 years of her life...

1500 RPM 8 Knots
2200 RPM 10 Knots
2600 RPM 15 Knots
3000 RPM 19-20 Knots
3500 RPM 25 Knots
4000RPM 27 knots (only done twice in the past 8 years, once to see what it would do, the other to get under a bridge and escape a storm on Lake Ontario (else ride it out for another half hour)).

Several people commented that their numbers are similar, including at least one person with an F30....